Abstract: Very low frequency (VLF) high voltage (HV) sinusoidal electrical test waves provide for testing AC electrical power installations and equipment having large electrical capacitances. VLF HV sinusoidal electrical waves are suitable for testing characteristics and/or qualities of insulation on long, buried electric power cables. Capacitance of a load being tested by VLF HV sinusoidal waves is discharged during a second half of each positive half-wave and during a second half of each negative half-wave by using a sequence of resistive discharge paths. Each successive discharge path in a sequence has less resistance than its predecessor for creating a sequence of progressively-reduced discharge Time Constants. Solenoid-operated switch contacts bring successive discharge paths into action. Also, solenoid-operated switch contacts reverse polarity to create positive and negative half waves of the VLF HV sinusoidal electrical test waves.

Abstract: An in-line buck/boost voltage/regulating apparatus and system for delivering AC electrical power of regulated voltage from an output terminal of a main winding to an electrical load. The apparatus has an input terminal for connection to an AC power supply and comprises first, second and third ferromagnetic transformer cores having first, second and third cross-sectional areas, respectively; and these cross-sectional areas have relative sizes of X square units, Y square units and Z square units, respectively. There are first, second and third regulator windings respectively mounted on the first, second and third cores, and electromagnetically coupled with their respective cores. The first, second and third windings have first, second and third numbers of turns, respectively. Switching elements selectively connect the first, second and/or third windings across the AC supply and selectively short-circuit any of the first, second and/or third windings which are not connected across the AC supply.

Abstract: A continuously variable voltage direct current power supply having first and second output terminals is provided using a variable transformer with a core of magnetically permeable material encircled by at least one electrical winding, with segments of winding turns being exposed along two spaced traverse paths. First and second electrically conductive brushes are simultaneously movable along these respective paths, with at least one brush at all times contacting an exposed segment. Rectifiers connect the first brush to the first output terminal and the second output terminal to said first brush. Rectifiers connect the second brush to the first output terminal and the second output terminal to said second brush. Rectifiers connect a winding terminal to the first output terminal and the second output terminal to said winding terminal.

Abstract: In a variable transformer, two high-conductivity brushes are mounted in a carriage and adapted for longitudinally traversing the transformer winding to contact exposed segments of the winding. By relatively elevating and exposing the odd and even turns along two different traverse paths, contact with the individual odd and even turns is obtained by the dual brush system without short-circuiting adjoining turns, the brushes being interconnected through an external current-limiting or compensating circuit. Spacings between exposed segments of the winding along these respective traverse paths are filled with dielectric material and are wider than the high-conductivity brushes; thus these brushes can never short circuit adjacent turns. The brushes are positioned so that at all times at least one of them contacts an exposed winding segment.